Stock markets dropped sharply on Tuesday in response to concern about the deal President Trump claimed on Twitter to have made with China. Part of the problem was that Trump’s presentation of what happened differed from what China claimed, and that uncertainty eroded confidence among investors.

It used to be that Trump heralded the movement of the markets as validation of his expertise on the economy. Over the course of 2017, Trump tweeted about the stock markets scores of times, always in laudatory terms. His adviser Kellyanne Conway, at one point early in his administration, pronounced that a record close on the Dow Jones industrial average reflected that “markets continue to like the policies, action and vision” of Trump. When Republicans passed a bill cutting corporate taxes last December, Trump promised it was going to goose markets higher.

The news from the Financial Markets is even better than anticipated. For all of you that have made a fortune in the markets, or seen your 401k’s rise beyond your wildest expectations, more good news is coming!

But over the course of 2018, that hasn’t happened. At close on Tuesday, both the Dow Jones industrial average and the Standard & Poor’s 500-stock index were about where they’d started the year. In the first 12 months after the tax-cut bill, the markets had been mostly flat. This wasn’t the economic “rocket fuel” Trump once promised the tax cuts would be.

Not only did Trump celebrate market gains as proof of his effectiveness last year, he also used stock prices to criticize Barack Obama during his predecessor’s administration.

The stock market and US dollar are both plunging today. Welcome to @BarackObama’s second term.

To the same point in the second year of Obama’s first term, though, both the Dow and S&P 500 saw bigger percentage-point gains than the markets have seen under Trump, by far.

(Philip Bump/The Washington Post)

The Dow and S&P 500 are much higher now than they were eight years ago, but, even so, each index increased by more points over the course of Obama’s second year in office than in 2018. (December 4, 2010, was a Saturday, so this uses Friday’s closing prices.)

(Philip Bump/The Washington Post)

The tepid market growth in 2018 has also meant that one of Trump’s most-prized talking points, about market growth under his administration, itself compares unfavorably with Obama. Since each president’s inauguration, markets grew more robustly in 2009 and 2010 than from Trump’s inauguration to Tuesday.

(Philip Bump/The Washington Post)

In terms of actual point value, the markets have grown more during Trump’s administration. Higher values also mean bigger variations; several of the biggest single-day drops in the Dow have come during Trump’s presidency.

(Philip Bump/The Washington Post)

A lot can change quickly on Wall Street, so Trump’s 2018 can still turn around.

Whether it’s useful to track presidential success by watching the variations of stock prices is another question entirely, of course. But we’re not the ones who spent 2017 establishing that as a metric by which to judge Trump — or spent years under Obama using market prices as a cudgel.